Santa Clara County, CA. Five residents of Santa Clara County have been infected with West Nile virus (WNV). Two residents had the more severe neuroinvasive form of the disease, West Nile encephalitis, one had West Nile fever, and two residents had no symptoms. Of the three people with symptoms, two were hospitalized and released, and one is currently hospitalized. All five Santa Clara County residents live in areas of the county with high WNV activity this year - see the map on page 2 or visit http://bit.ly/Y9MWLM, which shows fogging zones areas where mosquitoes infected with WNV have been detected. Unlike last year, when WNV activity in birds and mosquitoes was concentrated in Milpitas and East San Jose, this year WNV activity is concentrated in Mountain View, Sunnyvale, Santa Clara, Cupertino, Campbell, west and south San Jose.

"It is important to remember most people who get a mosquito bite will not become infected, will not develop symptoms and will not need to seek care," said Dr. Sara Cody, Health Officer for Santa Clara County. "But in some cases, West Nile can cause serious illness. To reduce the risk of West Nile, residents should take precautions to avoid being bitten by mosquitoes."

This year Santa Clara County has had an unusually large number of birds that died from WNV. At this time 648 dead birds infected with WNV have been reported in Santa Clara County (2014), which represents half of all the reported dead birds infected with WNV in California. 85% of the dead birds tested in the County this year were infected with WNV. Because of this situation, the risk of WNV in residents of Santa Clara County is likely to be higher than in previous years, especially over the next two months.

Last year there were two human cases of WNV; there was one case in 2011, which was fatal, one case in 2008, four in 2007, and five in 2006.

Physicians in Santa Clara County have been provided information regarding the symptoms of West Nile virus, how to diagnose the disease and to report suspected cases to the Public Health Department.

WNV is transmitted to humans and animals through the bite of an infected mosquito. The risk of becoming seriously ill is low for most people. Less than 1% of people can develop serious neurologic illness such as encephalitis or meningitis. People over the age of 50 have a higher chance of becoming ill. In addition, people with diabetes or hypertension have a greater risk of complications and serious illness.

After someone is bitten, the incubation period is generally 2 to 6 days, but it can be as many as 14 days. Most people are infected between June and September, when it is warm outside and mosquitoes are most active. People can take steps to protect themselves from contracting West Nile Virus, including: